Effects of photodynamic therapy using verteporfin on experimental choroidal neovascularization and normal retina and choroid up to 7 weeks after treatment

Purpose. To study the long-term effects of photodynamic therapy (PDT), using liposomal benzoporphyrin derivative (BPD) or Verteporfin, on experimental choroidal neovascularization (CNV) and on normal retina and choroid (with no CNV) in the cynomolgus monkey eye. Methods. Photodynamic therapy was performed in 8 cynomolgus monkey eyes with experimental CNV induced by laser injury. The effect of PDT on normal retina and choroid (with no CNV) was studied in 9 monkey eyes. Liposomal BPD was administered intravenously (0.375 mg/kg) either as a bolus, as a slow infusion over 32 minutes, or as a fast infusion over 10 minutes. Photodynamic therapy was performed using light at a wavelength of 689 or 692 nm, with an irradiance of 600 mW/cm² and fluence of 150 J/cm². Follow-up studies, including fundus photography and FA, were performed at 24 hours after PDT and then weekly. Indocyanine green and BPD angiography were performed in selected cases. Tissues were examined with light and electron microscopy at the end of follow-up. Results. Twenty-three of the 32 areas of CNV treated with PDT showed absence of angiographic leakage at 24 hours. Twenty-eight areas of CNV were followed for 4 weeks, 22 of 28 showed absence of angiographic leakage at 2 weeks, and 20 of 28 at 4 weeks of follow-up. Forty spots on the normal retina and choroid were treated with PDT and were followed for 4 to 7 weeks. These spots showed pigment-laden cells in the outer retina, variably pigmented retinal pigment epithelium (RPE) in the treated area, intact neurosensory retina, and reperfusion of the choriocapillaris. Conclusions. Photodynamic therapy leads to absence of angiographic leakage for at least 4 weeks in experimental CNV in the monkey model. In the normal monkey eye the RPE and choriocapillaris show generalized recovery with preservation of the neurosensory retina 7 weeks after PDT.